1. Field of the Invention
The present invention relates to a dial device for an illumination meter and more specifically to an illumination meter dial device on which black or dark (deep colored) indication marks are recognized in contrast with a white or bright (light colored) dial plate irrespective of when illuminated or not illuminated from inside.
2. Description of the Prior Art
Various meters such as speedmeter, fuel meter, etc. are mounted on automotive vehicles. In these meters, conventionally, the dial is usually made of an opaque material and indication marks such as graduation marks, numerals, characters, etc. are made of a transparent material. In use, the dial is illuminated from the back side of the dial plate so that the transparent indication marks can be seen from the front of the meter.
On the other hand, the same applicant has already disclosed a meter dial such that the dial plate is formed of a dark semitransparent layer and the indication marks are formed of a transparent layer so as to reduce a difference in brightness between the dial plate and the indication marks for prevention of fatigue of driver's eyes (in Japanese Published Unexamined (Kokai) Application No. 62-190416).
Recently, however, there exists a demand for old-fashioned meters provided with a white dial and black indication marks in the accompany with a tendency toward the retrospective request or the simplicity of meters. In the case of the conventional meters of this type, since it is impossible to illuminate the dial plate from the back side of the dial plate, the indication marks are illuminated only from outside at night. In other words, when the white dial is illuminated from inside, it is difficult to recognize the indication marks in contrast with the illuminated white dial plate. In particular, when the dial is illuminated from inside in twilight, since light irradiated upon the dial plate from outside is balanced with that illuminated from inside, there exists a problem in that it is impossible to recognize the indication marks formed on the dial plate in the case of the white dial formed with dark marks.